Most Repeated MDCAT Biology MCQs

1. 1

   Repeated 13×Support and Movement

   The muscles attached to the bones are

   • AVoluntary and smooth
   • BInvoluntary and smooth
   • CVoluntary and striated✓
   • DInvoluntary and striated
   • ESmooth and striated

   Explanation

   Voluntary muscles are under conscious control, allowing us to move our bodies intentionally. Striated muscles have a striped appearance under a microscope due to the organization of their contractile proteins, giving them the name "striated." These muscles are also known as skeletal muscles and are responsible for body movements.

   Appeared in past papers: 2010, 2011

2. 2

   Repeated 11×Cell Structure and Function

   The finger like infoldings, which are formed by inner membrane of mitochondria, are called:

   • ARibosomes
   • BMatrix
   • CPorin
   • DCristae✓

   Explanation

   The correct answer is Cristae, which are the finger-like infoldings of the inner membrane of mitochondria. These structures are critical for the mitochondria's function, as they increase the surface area available for the electron transport chain, thereby enhancing ATP production.In contrast, Ribosomes are involved in protein synthesis and do not relate to mitochondrial structure. The Matrix refers to the space within the mitochondria, but it does not describe any infoldings. Porin is a type of protein that allows for the transport of substances across membranes and is not an infolding structu

   Appeared in past papers: 2019

3. 3

   Repeated 11×Cell Cycle

   Cell death due to tissue damage is called:

   • ANecrosis✓
   • BMetastasis
   • CApoptosis
   • DEpistasis

   Explanation

   [A] Necrosis is the death of a body tissue,occurring when too little blood flows to the tissue.[B]Metastasis means that cancer has spread to different parts of body[C] Apoptosis the process of programmed cell death[D] Epistasis is a circumstance where the expression of one gene is modified by expression of one or more gene

   Appeared in past papers: 2010, 2011, 2013, 2023

4. 4

   Repeated 9×Cell Structure and Function

   The ability to distinguish between two separate points/objects is:

   • AMagnification
   • BFractionation
   • CCentrifugation
   • DResolution✓

   Explanation

   Scientists think of resolution as the ability to tell that two objects that are very close together are distinct objects rather than just one.Fractionation is a separation process in which a certain quantity of a mixture (gas, solid, liquid, enzymes, suspension, or isotope) is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient.Centrifugation is a technique used for the separation of particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed. The particles are

   Appeared in past papers: 2018

5. 5

   Repeated 9×Coordination and Control

   The autonomic nervous system controls all of the following activities except:

   • ADigestion of food
   • BHeart beat
   • CContraction of pupil of eye
   • DThought✓
   • EBreathing rate

   Explanation

   The autonomic nervous system does not directly control thought processes. Thought is primarily regulated by the central nervous system, which includes the brain and spinal cord. While the autonomic nervous system can be influenced by certain thought patterns, such as stress or relaxation, it does not directly control the generation or content of thoughts.

   Appeared in past papers: 2011, 2014, 2015

6. 6

   Repeated 9×Variation and Genetics

   A woman with normal colour vision, whose father was red green colour blind, married a red green colour blind man. What is the probability of her born child being red green colour blind?

   • A1.0
   • B0.75
   • C0.50✓
   • D0.25

   Explanation

   Males have 1 X chromosome and 1 Y chromosome, and females have 2 X chromosomes. The genes that can give you red-green colour blindness are passed down on the X chromosome.The woman’s father is red-green colour blind. Since the woman got one of her X chromosomes from her father this means that she is a carrier. As it can be seen from the table the probability of having a colourblind child is 0.5%

   Appeared in past papers: 2017

7. 7

   Repeated 9×Coordination and Control

   The absorption and use of calcium are regulated by:

   • AParathormone✓
   • BAdrenaline
   • CThyroxin
   • DThiamin
   • EProlactin

   Explanation

   Circulating parathyroid hormone targets the distal convoluted tubule and collecting duct, directly increasing calcium reabsorption.

   Appeared in past papers: 2015

8. 8

   Repeated 8×Cell Structure and Function

   The structure present in a eukaryotic cell but absent in prokaryotic cells is:

   • ANucleus✓
   • BDNA
   • CRibosomes
   • DCell surface membrane

   Explanation

   The correct answer is the nucleus. It is a hallmark of eukaryotic cells, encapsulating the cell's genetic material within a distinct, membrane-bound structure. Prokaryotic cells lack this feature; their genetic material is dispersed within the cell without a surrounding nuclear membrane. The other options are common to both cell types: DNA is present in all cells as the genetic blueprint, ribosomes are universal sites of protein synthesis, and the cell surface membrane is fundamental to maintaining cellular integrity and homeostasis.

   Appeared in past papers: 2019

9. 9

   Repeated 8×Gaseous Exchange

   During breathing, air from pharynx enters to:

   • ATrachea✓
   • BBronchioles
   • CAlveoli
   • DBronchi

   Explanation

   When you inhale through your nose or mouth, air travels down your pharynx (back of your throat), passes through your larynx (voice box) and into your trachea (windpipe). Your trachea is divided into two air passages called bronchial tubes. One bronchial tube leads to your left lung, the other to your right lung.

   Appeared in past papers: 2018

10. 10

    Repeated 8×Biotechnology

    Which kind of therapy was given in 1990 to a four­ year­ girl with Adenosine Deaminase (ADA) enzyme deficiency?

    • AGene therapy✓
    • BChemotherapy
    • CImmunotherapy
    • DRadiation therapy

    Explanation

    Gene therapy was the treatment given in 1990 to a four-year-old girl with Adenosine Deaminase (ADA) deficiency. This type of therapy focuses on correcting genetic problems by inserting genes into a patient's cells. In the case of ADA deficiency, gene therapy was used to insert a healthy copy of the ADA gene into the child's cells to compensate for the defective gene, thereby restoring the function of the enzyme. On the other hand, chemotherapy, immunotherapy, and radiation therapy are primarily used for cancer treatment and are not applicable for treating genetic enzyme deficiencies.

11. 11

    Repeated 8×Support and Movement

    What do we call the cell surface membrane of a muscle fibre?

    • ASarcolemma✓
    • BPlasma membrane
    • CSarcoplasm
    • DMyofibrils

    Explanation

    The correct answer is Sarcolemma. The sarcolemma is the specialized cell membrane that surrounds a muscle fiber. It is crucial for communication between the nervous system and the muscle fiber, allowing the initiation of muscle contraction through electrical signal transmission. The term 'sarco-' denotes its association with muscle cells, differentiating it from the general plasma membrane found in all cell types. Option B, the 'Plasma membrane', refers to the cell membrane in general terms and does not specify its role in muscle cells. Option C, 'Sarcoplasm', is the cytoplasmic content of the

    Appeared in past papers: 2020, 2023

12. 12

    Repeated 8×Biological Molecules

    In which of the following is the organic compound COOH (carboxyl) group found? (I) Carbohydrate (II) Lipid (III) Protein

    • AI only
    • BII only
    • CI and II only
    • DII and III only✓
    • EI , II and III

    Explanation

    Carboxyl groups are commonly found in amino acids, fatty acids, and other biomolecules. Whereas carbohydrates only contain atoms of carbon hydrogen and oxygen they don't have any functional group.

    Appeared in past papers: 2015

13. 13

    Repeated 8×Coordination and Control

    Gigantism in human beings is caused due to over secretion of:

    • AThyrotropin
    • BCorticotropin
    • CSomatotropin✓
    • DProlactin

    Explanation

    Gigantism occurs when a child’s pituitary gland makes too much growth hormone, which is also known as somatotropin. Corticotropin-releasing hormone (CRH), also called corticotropin-releasing factor (CRF), is a peptide hormone that activates the synthesis and release of adrenocorticotropic hormone (ACTH) from the pituitary gland. In this way, CRH affects our response to stress, addiction and depression, amongst others. Prolactin is a hormone made by the pituitary gland, a small gland at the base of the brain. Prolactin causes the breasts to grow and make milk during pregnancy and after birth. T

    Appeared in past papers: 2017

14. 14

    Repeated 7×Biological Molecules

    Which of the following holds the alpha helix of protein in its place:

    • AR group
    • BDisulfide bond
    • CAmino group
    • DHydrogen bond✓

    Explanation

    The α-helix is a right-handed helix with the peptide bonds present on the inside and the side chains extending outward. It is stabilized by the regular formation of hydrogen bonds parallel to the axis of the helix; they are formed between the amino and carbonyl groups of every fourth peptide bond.

    Appeared in past papers: 2018

15. 15

    Repeated 7×Homeostasis

    The external solution having more concentration than the cell sap is known:

    • AHypertonic solution✓
    • BHypotonic solution
    • CIsotonic solution
    • DNone of these

    Explanation

    The correct answer is a hypertonic solution. In osmoregulation, when a cell is placed in a hypertonic solution, the external environment has a higher concentration of solutes compared to the inside of the cell. This concentration difference causes water to move out of the cell through osmosis, leading to a decrease in cell volume and potential plasmolysis. Conversely, a hypotonic solution would cause water to move into the cell, and an isotonic solution would result in no net water movement. None of these is incorrect because the correct term for a solution with higher solute concentration tha

16. 16

    Repeated 7×Kingdom Prokaryote

    Rod-shaped bacteria are known as:

    • ACocci
    • BBacilli✓
    • CSpirilla
    • DNone of these

    Explanation

    Bacteria are classified according to their shape, or morphology. Spherical bacteria are known as cocci, rod-shaped bacteria are bacilli, and spiral-shaped bacteria are spirilla.

    Appeared in past papers: 2018

17. 17

    Repeated 7×Biotechnology

    What forms the basis of DNA fingerprinting?

    • AThe relative proportions of purines and pyrimidines in DNA
    • BThe relative difference in the DNA occurrence in blood, skin, and saliva
    • CThe relative amount of DNA in the ridges and grooves of the fingerprints
    • DSatellite DNA occurring as highly repeated, short DNA segments✓

    Explanation

    DNA fingerprinting is a technique of determining nucleotide sequences of certain areas of DNA which are unique to each individual. The difference of about 0.1% or 3 × 106 base pairs (out of 3 × 10 9 bp) provides individuality to each human being. The human genome possesses numerous small noncoding but inheritable sequences of bases that are repeated many times. These sequences occur near telomere, centromeres, Y chromosome, and heterochromatic area. The area with the same sequence of bases repeated several times is called repetitive DNA. It is separated as a satellite from the bulk DNA during

18. 18

    Repeated 7×Coordination and Control

    Piriformis syndrome is associated with which of the following disorder:

    • AArthritis
    • BSciatica✓
    • CSpondylosis
    • DDisc slip

    Explanation

    Piriformis syndrome is a condition where the piriformis muscle in the buttocks compresses the sciatic nerve, leading to sciatica symptoms such as pain, numbness, and tingling in the lower limbs. While a slipped disc can also cause sciatica, piriformis syndrome is specifically related to muscle compression rather than disc issues. Arthritis and spondylosis, on the other hand, are primarily joint and spinal disorders that do not typically involve the piriformis muscle or cause sciatica directly.

    Appeared in past papers: 2018

19. 19

    Repeated 7×Support and Movement

    Which of the following bones are present in the palm of the hand:

    • ACarpals
    • BMetacarpals✓
    • CPhalanges
    • DTarsal
    • ERadius

    Explanation

    The human forelimbs each consist of 30 bones: The humerus, which forms a ball and socket joint with the scapula, and two long parallel bones, the radius and ulna, at its distal end. The radius and ulna join the wrist with eight small carpal bones, which articulate with five metacarpals of the palm. From the palm extend the fingers containing 14 small bones called phalanges, arranged in 5 rows, one row in each finger. The relevant detail for this question is that the bones of the palm are called metacarpals, hence option B is correct.

    Appeared in past papers: 2010

20. 20

    Repeated 6×Variation and Genetics

    The Law of Dominance Is illustrated in the garden pea by:

    • AHomozygous tall x heterozygous tall
    • BHeterozygous tall x heterozygous tall
    • CHomozygous tall x homozygous tall
    • DPure short x pure short
    • EHomozygous tall x pure short✓

    Explanation

    The Law of Dominance states that in a heterozygous individual, the dominant allele will determine the phenotype while the recessive allele is masked. In this case, the cross between a homozygous tall plant (TT) and a pure short plant (tt) clearly illustrates this law, as all offspring (Tt) will be tall, demonstrating that the dominant allele 'T' expresses itself over the recessive 't'.The other options do not adequately illustrate the Law of Dominance: the first option shows both parents expressing the tall phenotype, while the second option leads to a mix of phenotypes. The third option resul

    Appeared in past papers: 2010, 2011

21. 21

    Repeated 7×Coordination and Control

    How many meninges cover the human brain?

    • A5
    • B4
    • C3✓
    • D2
    • E1

    Explanation

    There are three layers of meninges around the brain and spinal cord. The outer layer, the dura mater, is tough, white fibrous connective tissue. The middle layer of meninges is the arachnoid, a thin layer resembling a cobweb with numerous threadlike strands attaching it to the innermost layer.

    Appeared in past papers: 2014

22. 22

    Repeated 5×Reproduction

    Referring to sexual reproduction, humans are:

    • AHermaphrodites
    • BVivaparous✓
    • COviparous
    • DSelf-fertilized

    Explanation

    The main difference between oviparous and viviparous animals is that oviparous animals do not undergo any embryonic development inside the mother whereas viviparous animals develop into young animals inside the mother. This means oviparous animals lay eggs. These eggs develop and hatch into young individuals.A hermaphrodite is an organism with both male and female genitalia. In sexually reproducing organisms, males have organs that produce male gametes, usually sperm. Sometimes the genders pair off equally, one male for one female. Other times, one male or female will breed with a large group

    Appeared in past papers: 2018, 2023

23. 23

    Repeated 7×Miscellaneous

    Which of the following diseases is sexually transmitted?

    • ATuberculosis
    • BAIDS✓
    • CDengue Fever
    • DCholera

    Explanation

    Acquired immunodeficiency syndrome (AIDS) is a chronic, potentially life-threatening condition caused by the human immunodeficiency virus (HIV). By damaging your immune system, HIV interferes with your body's ability to fight infection and disease. You can get HIV from contact with infected blood, semen, or vaginal fluids. Most people get the virus by having unprotected sex with someone who has HIV. Another common way of getting it is by sharing drug needles with someone who is infected with HIV. Hence, Option B is correct. Tuberculosis is caused by bacteria that spread from person to person t

    Appeared in past papers: 2020

24. 24

    Repeated 7×Enzymes

    Some enzymes require the presence of a non protein molecule to behave catalytically. An enzyme devoid of this molecule is called a(n):

    • AHoloenzyme
    • BApoenzyme✓
    • CCoenzyme
    • DZymoenzyme

    Explanation

    Enzyme with a non-proteinous part is called Holoenzyme; without that non-proteinous part, it is called Apoenzyme.

25. 25

    Repeated 7×Transport

    Regarding structure of the human heart, Chordae tendinae are present in:

    • AAtria
    • BPulmonary valve
    • CVentricles✓
    • DAortic valve

    Explanation

    Chordae tendineae (or simply chordae) are fibrous cords or tendons that are present in the heart to anchor the atrioventricular (AV) valves (specifically, the tricuspid and bicuspid/mitral valves) to the papillary muscles located in the ventricles. This prevents the valves from inverting into the atria when the ventricles contract and helps in maintaining proper valve function. Therefore, the correct location for chordae tendineae is Ventricles

    Appeared in past papers: 2020, 2023

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